1. Field of the Invention
This invention relates to a steering wheel positioner for an automatic driving position system used for adjusting a steering wheel automatically into a memorized steering wheel position suitable for respective drivers in accordance with a positioning operation of a memory switch in a motor vehicle, for example.
2. Description of the Prior Art
Heretofore, there has been used an automatic driving position system as shown in FIG. 4.
The automatic driving position system 100 illustrated in the drawing is so designed as to drive a steering wheel shaft 103 through an actuator 102 between the upper position A and the lower position B in accordance with a manual operation of a positioning switch 101.
The actuator 102 is connected with a controller 105 housed with a microcomputer, and the controller 105 is connected with a battery 106.
The controller 105 is connected with a seat-driving motor 108 for driving a seat 107 back and forth, up and down, and adjusting a reclining angle of a seat back of the seat 107, and the controller 105 is input with steering wheel position data representing an inclination angle of the steering wheel shaft 103 detected by a tilt sensor 109, seat position data detected by a seat sensor 110 and car speed data detected by a car speed sensor 111 and having pulse frequency proportional to the actual traveling speed of the vehicle through an interface circuit (not shown).
A steering wheel 104 is mounted with an air bag module 112 (air bag system) on a steering wheel hub 104a thereof so as to reduce impulsive force to be applied on the driver at the time of a frontal crash of the vehicle by expansion of the air bag module 112.
In case of memorizing the driving position suitable for the driver the steering wheel 104 is moved into the position suitable for the driver by working the actuator 102 and adjusting the inclination angle of the steering wheel shaft 103 according to the manual operation of the positioning switch 101, and the seat 107 is moved into the position suitable for the driver by working the seat-driving motor 108 in accordance with an operation of a manual switch disposed on a switch board (not shown). The microcomputer in the controller 105 memorizes the steering wheel position and the seat position suitable for the driver as the steering wheel position data representing the inclination angle of the steering wheel shaft 103 detected by the tilt sensor 109 and the seat position data detected by the seat sensor 110 by a setting operation of a set switch disposed on the switch board in this state.
After this, the steering wheel 104 and the seat 107 move automatically to the respective suitable positions memorized by the microcomputer through the actuator 102 and the seat-driving motor 108 according to a positioning operation of a memory switch disposed on the switch board.
In addition to above, the steering wheel 101 is so designed as to be driven upwardly to the highest position C (turnout position) automatically when the vehicle is stopped and an ignition key is pulled out from an ignition switch of the vehicle, for example, that the steering wheel 104 may not preclude the driver from leaving the driver's seat and sitting down in it. When the driver sits down in the driver's seat of the vehicle and inserts the ignition key into the key hole of the ignition switch, for example, the steering wheel 104 is so designed as to be returned automatically to the memorized position suitable for the driver.
In case of detecting abnormality in the tilt sensor 109 from one cause or another, the steering wheel 104 is controlled so as to be moved into the lower position B shown in FIG. 4 by working the actuator 102 to the fullest measure in the descending direction of the steering wheel shaft 103 because the tilt sensor 109 can not detect the inclination angle of the steering wheel shaft 103 and it is impossible to return the steering wheel 104 to the suitable position memorized by the microcomputer. At this time, it is not impossible to move the steering wheel 104 to the turnout position C by working the actuator 102 sufficiently in the ascending direction of the steering wheel shaft 103, however it is not possible to operate the steering wheel 104 at the turnout position C and not possible to reduce effectively the impulsive force to be applied on the driver even if the air bag module 112 works by the frontal crash of the vehicle in such a case.
If the abnormality of the tilt sensor 109 is caused when the vehicle is traveling, the controller 105 prevents the actuator 102 from driving the steering wheel shaft 103 in the downward direction while the vehicle is traveling, and shifts the steering wheel shaft 103 into the lower position B through the actuator 102 after the vehicle is stopped so as not to obstruct safety in the driving of the vehicle.
However, the aforementioned conventional automatic driving position system 100 is so structured as to Judge whether the vehicle is stopped or not by detecting existence of the car speed signal output from the car speed sensor 111, therefore the controller 105 misjudges the vehicle to be stopped when the car speed signal from the car speed sensor 111 disappears owing to disconnection or failure of the car speed sensor 111, or the vehicle speed decreases and a pulse interval of the car speed signal output from the car speed sensor 111 becomes longer.
Accordingly, there is a problem since the steering wheel shaft 103 shifts independently into, the lower position B shown in FIG. 4 even though vehicle is traveling in the cases as mentioned above.